It is well known to administer powdered medicament to the lung bronchioles of a patient by means of inhalation devices having mouthpieces which enable the medicament to be inhaled through the mouth of the patient. The medicament is supplied in capsules which are inserted in the device and pierced prior to use after which inhalation through the mouthpiece will cause the powdered medicament to be released from the capsule and passed to the patient. An object of the present invention is to provide an improved such inhalation device which is particularly, but not exclusively, suitable for use in the treatment of asthmatic patients.